In recent years, following an increase in the degree of density and integration of hybrid ICs and printed circuit boards carrying transistors, ICs, memory elements, and other electronic components, various thermally conductive silicone grease compositions have been used to provide high-efficiency heat dissipation from the aforementioned objects. In order to reduce flowability, such thermally conductive silicone grease compositions are filled with thermally conductive fillers. Recently, however, demands have arisen for improving thermal conductivity of the grease by increasing the density of the thermally conductive filler. For example, Japanese Unexamined Patent Application Publication (hereinafter referred to as “Kokai”) 2004-262972 discloses a thermally conductive silicone grease composition comprising an organopolysiloxane, a thermally conductive filler, and at least two kinds of methylpolysiloxanes having hydrolysable groups. Furthermore, Kokai 2008-019426 discloses a thermally conductive silicone grease composition comprising an organopolysiloxane having a specific structure, and organopolysiloxane acting as a wetter and having a triorganooxysilyl group on one of its terminals connected through an alkylene group, and a thermally conductive filler. Kokai 2009-138036 discloses a thermally conductive silicone grease composition comprising a siloxane oligomer having trialkoxysilyl groups and alkenyl groups, a thermally conductive filler having three different average particle sizes, a platinum-based catalyst, an organohydrogenpolysiloxane, and an isoparaffin solvent.
However, when in order to improve thermal conductivity the aforementioned thermally conductive silicone grease compositions are compounded with a large amount of a thermally conductive filler, the obtained compositions acquire a high coefficient of friction, and when the filler is supplied through a volumetric feeder, the latter is subject to abrasive wear, and the wear products contaminate the obtained composition.
It is an object of the present invention to provide a thermally conductive silicone grease composition that is characterized by high thermal conductivity, excellent handleability, low coefficient of friction, and especially, of dynamic friction.